1. Field of the Invention
The present invention relates generally to a portable chain saw sharpener in which the sharpener is adapted to file or sharpen the cutting teeth of a chain saw as well as the depth gauge members of the chain saw. In particular, the present invention is directed to a chain saw sharpener, in which the cutting surfaces of the teeth of a saw chain are conveniently sharpened quickly without removing the chain from the chain bar.
2. Description of the Prior Art
Chain saws are normally employed in logging operations for the harvesting of timber. The cutting chain of a chain saw is constructed from riveted metal sections and features sharp cutting teeth. The cutting teeth of the chain saw have two cutting surfaces: one perpendicular to the saw kerf and the other parallel to the saw kerf.
The cutting chain of the chain saw also features a depth gauge or “raker” that rides ahead of each cutting tooth. The height of the rakers in relationship to the cutting teeth controls the depth of the cut made by the cutting teeth. For example, if the raker is too high, the tooth will not cut and if the raker is too low, the tooth will cut too deeply. Therefore, maintaining the height of the rakers is important for proper functioning of a chain saw.
Maintaining the sharpness of a chain saw is particularly important for maintaining cutting efficiency and for preventing injuries caused by snagging of the chain as a result of dull cutting teeth. It is well known that a saw chain can become dull quite quickly when the chain saw is used for moderate to heavy jobs, and it is not uncommon for the chain in heavy use to require sharpening twice in one day. Therefore, a method and apparatus for sharpening a saw chain quickly and conveniently is important to minimize down time on any particular job. It is preferable that the saw chain be sharpened without removing the chain from the saw, in order to reduce the time and trouble necessary to sharpen the chain. In addition, it is desirable for the sharpener to be easily portable, so that the sharpener can be brought along to remote jobs where a chain saw is often used.
Large industrial sized machines are available for sharpening saw chains, but these devices require removing the chain from the saw and leaving the chain for sharpening by an experienced professional and waiting for a later pick-up. It is obvious that this method is time consuming and inconvenient, and requires the intensive chain saw user to keep a number of extra chains on hand so that in the field a sharp chain is readily available to replace a dull chain. Another disadvantage of machine sharpening is that it eats away the cutting blade of the chain saw every time the saw is sharpened. Usually, after machine sharpening the chain saw for 3 to 4 times, no functional blade is left.
A number of devices exist for sharpening the teeth of chain saws. For example, U.S. Pat. No. 4,416,169, “Automatic Saw Chain Grinder” to Silvey discloses a chain saw grinder which uses a grinding wheel rotated by a motor to grind the teeth of the chain saw. The chain saw advances over pulley wheels so that each tooth can be sharpened. A disadvantage of this type of sharpener is that the grinding wheel of the sharpener and cutting teeth of the chain both eventually become worn away. Moreover, the sharpener is not portable and the chain needs to be removed from the saw.
U.S. Pat. No. 5,156,071, “Chain Saw Sharpener with Built-up Grinding Tool” to Stevens discloses a chain saw sharpener that includes a sharpening tool constructed of a flat metal disc and an abrasive bead bonded along one side of the peripheral edge of the flat metal disc. The sharpening tool is supported between two support discs and is attached to the shaft of a motor for rotation about its axis. The chain saw sharpener of Stevens further employs a chain holder to clamp a chain saw chain to a semi-circular shaped holder during sharpening. The chain saw sharpener disclosed in Stevens is not easily portable and requires that the chain be removed from the saw in order to be sharpened.
Another type of chain saw sharpener is disclosed in U.S. Pat. No. 6,079,295, “Chain Saw Blade Sharpener with Stop” to Beard, Jr., in which the sharpening device includes a file mounting assembly, a clamping assembly, a chain stop and a circular file slidably coupled to the file mounting assembly. This type of sharpening device is helpful in maintaining the chain saw chain in place while sharpening. However, with this type of sharpener, the chain needs to be advanced manually and the file used for sharpening wears down more quickly.
U.S. Patent Application Publication No. 2009/0071297A1, “Chain saw Sharpening Tool” to Irwin discloses a chain saw sharpening tool that includes a barrel-shaped file guide and holder rigidly secured to one end of a round file and the opposite end of the file is connected to a power tool. Although this sharpening tool sharpens the cutting teeth of a chain saw, a separate file is required to adjust the height of the rakers after the sharpening of the cutting teeth.
Applicant's own U.S. Pat. No. 7,900,536, “Chain Saw Sharpener with Composite Wiskar” to Hensley, discloses a saw chain sharpener for a chain saw in which the bottom surfaces of the cutting teeth of a bottom sharpened chain saw are automatically sharpened by running the chain through the sharpener. The sharpener includes a sharpening device disposed in a recess of a housing attached removably to a chain saw and a lifting device for lifting the cutting teeth to a sharpening position. The sharpening device includes a sharpening wiskar, wherein the top surface of the sharpening wiskar is positioned to frictionally engage the bottom surface of the teeth to bottom sharpen the cutting teeth when the chain saw is operated.
The chain saw sharpeners described above have drawbacks such as they may not be easily portable, require a separate mounting and/or clamping assembly, require a separate file to adjust the height of the rakers, etc. Further, the known devices may require additional safety measures like a shield or a table vise to operate, wherein the present invention does not require such additional safety precautions to operate safely and reliably.